1. Field of the Invention
The invention relates to a system for use in detecting surface defects in manufactured parts and the like. More particularly, the invention relates to a system which enables an inspector to detect hairline cracks and flaws in otherwise inaccessible and remote locations through the use of ultraviolet light and fluorescent dye penetrant.
2. Description of Background Art
The use of dye penetrants to detect small flaws in critical manufactured components such as jet engine turbine blades is well known. Typically, flaw detection by the dye penetrant method requires the following sequence of steps.
First, the object to be tested is cleaned thoroughly, using a vapor degreaser, for example. Next the object is immersed in a dye penetrant solution which contains a solvent and a dye, typically one which fluoresces brightly when irradiated by long-wave ultraviolet radiation, in the approximate range of 300 nm to 400 nm. Alternatively, dye penetrant may be sprayed upon the surface of the object to be tested. Third, excess dye penetrant solution is removed from the surface of the part with the aid of another solution, and emulsifier. The part is then washed and dried. Finally, the part under test is illuminated with a source of ultraviolet radiation. Dye penetrant which has been entrapped in small voids such as cracks, seams or porous areas fluoresces brightly when illuminated by the ultraviolet radiation source, providing a visual indication of small defects which would otherwise escape visual detection. Sometimes a developer solution is applied to the surface of the part after that surface has been cleansed of excess dye penetrant solution. The function of the developer solution is to draw up to the surface of the part, by capillary action, dye which has been entrapped in voids some distance below the surface. This makes the dye and therefore the void more readily visible.
The dye penetrant inspection processes just described are generally effective for detecting small surface flaws in manufactured parts. However, minute cracks and flaws can exist in places which are inaccessible to conventional probes. Thus, the spray method of applying dye penetrant can miss remote hard-to-reach locations where cracks and flaws may exist. Although the immersion method of applying penetrant is more pervasive it has the drawback that the part to be tested must be preheated and remain immersed in the dye for a substantial period. A further drawback is that large and cumbersome parts require large immersion tanks and large volumes of dye penetrant solution.
Another disadvantage of fluorescent penetrant crack detection is several different instruments are required to accomplish each of the forementioned steps. After the dye penetrant is applied separate instruments are required to remove excess penetrant, to dry the surface to be examined, to apply the developer and to illuminate the surface to be examined with ultraviolet light for inspection. The manipulation and handling of these different instruments can be cumbersome and time consuming for a single operator.
Accordingly, it is an object of the invention to provide an interactive and reactive ultraviolet remote visual inspection system which allows for the detection of cracks in places not normally accessible to the eye.
It is a further object of the invention to provide a system of the type described in the previous paragraph wherein a single apparatus can be used for several different functions including illumination of the surface to be examined with white light, injection of dye penetrant, washing away of excess penetrant, drying the surface, injection of developer, illumination with ultraviolet light and visual inspection.
It is yet a further object of the invention to provide an apparatus of the type described in the previous paragraph which includes an articulated probe to facilitate visual inspection of remote internal areas such as passages in castings.
Additional objects and advantages of the present invention will be apparent to those skilled in the art by reading the accompanying specification and claims in view of the drawings.